On the day his son-in-law is set to testify before the Senate Judiciary Committee, President Donald Trump called on "beleaguered" Attorney General Jeff Sessions to investigate his presidential opponent.

The tweet is just the latest sign of tension between Trump and Sessions, a former Alabama Senator and one of the president's early endorsers and advisers. Last week, Trump told reporters he would not have appointed Sessions to lead the Justice Department if he'd been aware Sessions would recuse himself from the investigation into Russian influence in the 2016 presidential election.

Other presidential tweets from Monday centered on the Russian investigation.

Trump's son-in-law and chief adviser Jared Kushner is set to testify today before the Senate Intelligence Committee on his interactions with Russian officials during the presidential election. Kushner said he met with Russians at least four times but denies any collusion.